Disc drives are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of concentric data tracks. Typically, disc drives include a disc pack including a plurality of concentric discs mounted on a spindle motor which causes the disc to spin. The disc drive also includes head gimbal assemblies aligned with each disc surface. The head gimbal assemblies include a disc head slider which supports transducers or magnetoresistive elements for reading and writing data to the data tracks of the disc surfaces.
The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air onto the slider along the air bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the air bearing surface, the pressure between the disc and the air bearing surface increases, which creates a hydrodynamic lifting force that causes the slider to lift directly above the disc surface to read and write data to the surface of the discs.
Prior to rotation of the disc, the slider rests on the disc surface. The slider is not lifted from the disc until the hydrodynamic lifting force, caused by rotation of the disc, is sufficient to overcome a preload force supplied to bias the slider toward the disc surface. Thus, the hydrodynamic properties of the slider are affected by the speed of rotation of the disc, the design of the air bearing surface of the slider, and the preload force supplied to the head gimbal assembly.
Known discs include both landing zones and data zones on a disc surface. Data is stored in the data zone. Landing zones are used to support the slider when the disc drive is not in operation and provide a takeoff and landing surface for the slider. Landing zones contain no data because repeat contact by the slider would eventually destroy any data stored.
Textured landing zones are known which provide a roughened surface for reducing stiction between the slider and the disc surface for takeoff. Landing zones are also known which include bumps of different shapes and sizes formed on a disc surface by a laser technique or other technique to provide a surface for the slider to take off and land. Bumps provide lower contact area between the slider and disc surface to lower the stiction force holding the slider to the disc surface.
Disc drives are being designed which have lower slider fly heights. Disc storage space is also at a premium; and, thus, disc drives are designed to store data to edges of the data zone abutting the landing zone. Landing zones which are formed of bumps may interfere with the slider at lower fly heights when the slider is aligned to retrieve data at a transition zone at the edges of the landing and data zones. Interference of the slider with bumps at low fly heights may causes the bumps to deform, or may cause the head to crash. Bumps also interfere with the hydrodynamic air flow to the slider bearing surface, thus interfering with the flying characteristics of the slider. Repeat contact of the slider with the bumps during takeoff, and landing cause the bumps to deform under the stress of the slider over time, thus decreasing effectiveness of the bumps in reducing stiction.